This invention relates generally to fluid flow regulation systems and, more specifically, to an air-flow regulation system for a coal gasifier.
In a fixed-bed coal gasifier, such as the 42-inch, coal-fired, air-blown gasifier at the Morgantown Energy Technology Center, Morgantown, W. Va., air to support combustion is supplied by a reciprocating compressor through a surge tank. It is normal operating practice to supply air from the compressor to meet varying throughput requirements by means of valving within the compressor loading/unloading control system in a stepped manner. This results in pressure cycling at the compressor outlet. The cyclic pressure is somewhat dampened by the surge tank, but at the most severe conditions, the pressure can vary .+-.10 psi. This causes a .+-.5,000 standard cubic feet per hour (scfh) deviation in the normal operating flow of 80,000 scfh of air to the gasifier.
An attempt to control the air flow in a conventional manner using a conventional single proportional/integral controller with feedback did not provide adequate flow control (regulation). Solutions, such as installing a much larger surge tank or a pressure regulator, were found not to be practical. Thus, there is a need in this application for an easily implemented and economical means for regulating the air flow.